Not who you asked but I live in Poland and our self-checkouts are pretty flawless in my opinion. Simple combination of scale, bardcode scanner and touch screen and voila. Most shops that have them, have at least four of them. Supermarkets often have 6-8 and dedicated employee to oversee them, sometimes with their own touch screen and ability to bypass age checks or weight problems from their stand without moving to you.

They only scream if you scan something age-restricted or if weight doesn’t match. The second problem was much bigger in beginning, nowadays it’s actually rare.